Miter saw alignment system

ABSTRACT

A miter saw with an optical system for projecting an optical alignment marker onto a workpiece. The miter saw has a base, a turntable rotatably supported by the base, a fence disposed above the base for supporting the orientation of the workpiece located on the base, a support coupled to the rear portion of the turntable, and a cutting apparatus including a blade for cutting the workpiece. The cutting apparatus is pivotally coupled to the support for positioning the blade from a raised position above the workpiece to an operational position for engagement with the workpiece. The light projection system is attached to the cutting apparatus for projecting an optical alignment marker onto the workpiece so that the location at which the blade engages the workpiece is in a selectably adjustable relationship with respect to the position of the optical alignment marker on the workpiece. A belt-driven embodiment of the miter saw has an adjustable pulley system comprising a motor connected to a drive pulley, a blade pulley connected to the blade, the blade pulley being in substantial alignment with the drive pulley, and a belt for connecting the drive pulley with the blade pulley. An adjustment mechanism for adjusting the distance between the drive pulley and the blade pulley is provided so that the tension on the drive belt may be adjusted.

FIELD OF THE INVENTION

The present application relates to an alignment invention and a pulleysystem invention. The present alignment invention relates to a miter sawwith an optical alignment system, an more particularly, to a miter sawwith an optical system for projecting an optical alignment marker onto aworkpiece. The pulley system invention relates to a belt-driven mitersaw with an adjustable pulley system.

BACKGROUND OF THE INVENTION

In order to align the blade of a prior art miter saw with a cutting lineon a workpiece, the operator must typically lower the saw to determineif the blade is aligned with the cutting line. If necessary, the saw israised and the workpiece is maneuvered to improve the alignment, and thesaw-lowering procedure is repeated. When precision cutting is required,this procedure is extremely time-consuming, and the desired precision isoften not achieved, resulting in wasted time and material.

Further, miter saw blades have a discreet width. The cutting line, whichis generally a pencil mark on the workpiece, also has a discreet width,further complicating alignment. For example, if the blade is centereddirectly over the cutting line, the cut in the workpiece will beinaccurate by an amount approximately equal to half the width of theblade. Consequently, it is often difficult to determine precisely wherethe blade will engage the cutting line.

Belt-driven miter saws with fixed center pulley systems are known in theart. While belt-driven miter saws have the advantage of producing lessnoise and vibration than gear-driven systems, the fixed center pulleysystems used on prior art miter saws do not have the capacity tocompensate for stretching and wear of the drive belt. Once the drivebelt becomes stretched, it must be replaced. Further, the drive beltsused on fixed center pulley systems must be manufactured to a closetolerance because there is no capacity in the fixed center pulleysystems to adjust for manufacturing variation in the belt. Closetolerance belts tend to be more expensive to manufacture.

Another problem with fixed center pulley drive systems for miter saws isthat the blade pulley tends to interfere with the depth of cut possiblewith the miter saw. Ideally, a miter saw with a 10" diameter bladeshould be capable of cutting a nominal 2"×6" (typically having an actualcross-sectional size of 1-1/2"×5-1/2") workpiece when the blade isoriented at 90 degrees relative to the fence and a nominal 4"×4"(typically having an actual cross-sectional size of 3-1/2×3-1/2")workpiece when the blade is oriented at 45 degrees relative to thefence. However, known blade pulleys tend to be larger than the bladeflange used to anchor the blade to the miter saw, thereby reducing thedepth of cut possible with the blade. Previous attempts to use smalldiameter pulleys which that do not interfere with the cutting radius ofthe blade have resulted in extensive heat buildup on the pulley system,causing accelerated wear of the drive belt and damage to the pulleys.

SUMMARY OF THE INVENTION

The present alignment invention relates to a miter saw with an opticalsystem for projecting an optical alignment marker onto a workpiece. Theoptical system comprises a light projection system which is attached toa cutting apparatus for projecting a planar beam of light past one sideof the blade and onto the workpiece in order to form an opticalalignment marker on the workpiece. The optical alignment marker has athickness and two sides. The optical system comprises an adjustmentmechanism for adjusting the alignment marker so that the side of thealignment marker facing the blade is coincident with a plane defined byone side of the blade. The side of the linear alignment marker that iscoincident with the plane defined by the one side of the blade will thendesignate the location at which the one side of the blade will enter theworkpiece.

The preferred optical system may be used in connection with aconventional miter saw, generally having a base, a turntable rotatablysupported by the base, a fence disposed above the base for supportingthe orientation of the workpiece, a support coupled to the rear portionof the turntable, and a cutting apparatus including a blade for cuttingthe workpiece. The cutting apparatus is pivotally coupled to the supportfor positioning the blade from a raised position above the workpiece toan operational position for engagement with the workpiece.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 illustrates a perspective view of a preferred miter saw with anoptical alignment marker;

FIG. 2 illustrates the preferred laser source for generating the opticalalignment marker;

FIG. 3 illustrates a preferred adjustment system for adjusting theorientation of the light projection system of the present alignmentinvention;

FIG. 4 illustrates a top sectional view of a preferred belt-driven mitersaw with an adjustable pulley system; and

FIG. 5 illustrates a sectional view of a preferred adjustment mechanismfor use with a motorized belt-driven miter saw.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

FIG. 1 illustrates a miter saw 10 with a preferred optical alignmentmarker 12 projected onto a workpiece 14. While FIG. 1 illustrates thepreferred linear optical alignment marker 12, it will be understood fromthe discussion below that the optical alignment marker may be of a widevariety of configurations. The miter saw 10 preferably comprises a base16 having a work surface 18 for supporting the workpiece 14. A turntable20 is rotatably supported by the base 16. A fence 22 is disposed abovethe base 16 for supporting the orientation of the workpiece 14 locatedon the base 16. A support 24 is coupled by conventional means to therear portion of the turntable 20.

The miter saw 10 shown in FIG. 1 further comprises a cutting apparatus26 for cutting the workpiece 14. The cutting apparatus 26 generallycomprises a support arm 28 coupled to the support 24 by a supportcoupling 30 for positioning the cutting apparatus 26 between a raised,rest position and a lowered, operational position. A support spring 32(See FIG. 4) is enclosed within the support coupling 30 for biasing thecutting apparatus 26 to the raised, rest position. A motor 34 isconnected to a blade 36 by an adjustable pulley system 38 (See FIG. 5),which is concealed behind a belt housing 40. A cutter travel screw 42 isused to establish the maximum travel of the blade 36. A power cord 78 isprovided for powering the motor 34.

In its preferred configuration, the miter saw 10 will cut any angle froma 90° cut to 47° right or left. To adjust the angle of cut, a turntablehandle 44 is loosened, enabling the turntable 20 to be set at aparticular angle relative to the fence 22. The miter saw 10 ispreferably equipped with positive stops 46 at various intervals in orderto more securely retain the turntable 20 at particular angles.

The blade 36 is protected by a fixed upper blade 48 guard and a movablelower blade guard 50. When a cut is made to a workpiece 14, the lowerblade guard 50 automatically moves upward in order to expose the blade36 to the workpiece 14. The lower blade guard 50 rotates about a pivotlocated on the inside surface of the upper blade guard 48 (not shown).To operate the saw 14, the operator grasps a handle 52 and presses atrigger 54 (see FIG. 4) to activate the miter saw 14. The operator thenpresses the cutting apparatus 26 downward into the workpiece 14 so thatthe lower blade guard 50 is retracted and the blade 36 engages theworkpiece 14.

Those skilled in the art will recognize that many configurations ofmotorized miter saws are possible, including changes to the base,turntable, motor arrangements, guard arrangements, linkage arrangements,dimensions, and the like. The general configuration of the miter saw 10illustrated in FIG. 1 is set forth by way of example only.

FIG. 1 also illustrates portions of the preferred light projectionsystem 56 of the present alignment invention. The light projectionsystem 56 is preferably mounted in the front portion of the upper guard48 so as to minimize the amount of sawdust and other debris coming incontact with the system 56. In the preferred embodiment, the lower blade50 guard has a slit 58 in the front portion to allow the opticalalignment marker 12 to pass unobstructed to the workpiece 14. However,it will be understood by those skilled in the art that a number ofconfigurations are possible for orienting the light projection system 56of the present alignment invention. In particular, the light projectionsystem 56 may be attached to any suitable surface on the miter saw 14.

The preferred optical alignment marker 12 of the present alignmentinvention is of a generally linear configuration substantially parallelto the blade. The optical alignment marker 12 is preferably a beam ofcoherent visible light 0.030" wide. This configuration allows theoperator to align the optical alignment marker 12 with a cutting line 60on the workpiece 14. However, it will be understood that a variety ofoptical alignment marker configurations are possible. For example, thealignment marker 12 may be a series of dots, a cross-hair, a pair ofopposing arrows identifying one or both edge of the blade, etc.

The linear alignment marker has a the fan angle 62 which is preferablydetermined so that the linear alignment marker 12 has a length whichgenerally corresponds to the distance from the front to the rear of theturntable 20, when the cutting apparatus 26 is in the raised position.In the preferred embodiment discussed herein, a line generator creates afan angle of coherent laser light of approximately 35°, plus or minus 5°to insure that the linear alignment marker 12 will be focused generallyon the workpiece 14.

The preferred light projection system 56 of the alignment invention hastwo sensor lights, 64, 66, preferably on the front of the upper guard48, although the sensor may be located on any suitable surface. Thefirst sensor light 64 is preferably green and indicates that the lightprojection system 56 is operating. In the preferred embodiment, thelight projection system 56 and the first sensor light 64 arecontinuously activated whenever the miter saw 14 is plugged into anelectrical outlet, thereby signaling to the user that the saw 14 isplugged-in. It will be understood that the light projection system 56may alternatively be activated/deactivated by a switch or attenuated bysome mechanical means.

The second sensor light 66 is preferably red and indicates that thelight projection system 56 has shut off due to a high temperature or alow temperature condition. In the preferred light projection system 56of the present alignment invention, the red shut off light is triggeredwhen the ambient temperature is below -10° C. or above 48° C.

As will be discussed in detail below, the light projection system 56 ispreferably equipped with a series of adjustments for selectivelyadjusting the relationship of the blade 36 with respect to the positionof the optical alignment marker 12 on the workpiece 14. FIG. 1illustrates the preferred lateral adjustment mechanism, which comprisesa right push knob 68 and left push knob 70 (See FIG. 3). Lateralmovement of the light projection system is preferably limited by anupper end stop 72 and a lower end stop 74 (not shown) on each side ofthe upper blade guard 48.

FIG. 2 illustrates the electrical portion of the preferred lightprojection system 56 of the present alignment invention. A transformer(not shown) connected to the main power cord 78 converts standard housecurrent (110 volts AC) to preferably 5 volts (DC). The transformer isconnected by wires 80 to the control electronics (not shown), which arecontained within a sealed control box 84. The first and second sensorlights, 64, 66, discussed above, are mounted to the control box 84. Alaser barrel 86 with a pivot pin 88 contains a laser source 90, which isconnected to the control electronics.

The laser 90 is preferably a visible laser diode with 5.0 milliwattsmaximum output and a wavelength of 620 to 680 nanometers. Governmentregulations require that the laser comply with FDA 21 CFR 1040.10 and1040.11 class IIIA laser products. It will be understood by thoseskilled in the art that a variety of light projection systems 56 arepossible, and that it is possible to use a non-coherent light source. Itwill also be understood by those skilled in the art that to generate thepreferred linear alignment marker 12, the coherent laser light from thelaser preferably passes through a lens 92, which generates a pointsource of light. The point source of coherent laser light then passesthrough a spherical line generator 94 to generate the generally linearalignment marker 12.

FIG. 3 illustrates the preferred adjustment mechanism 96 for adjustingthe special relationship between the optical alignment marker 12 and theblade 36. The light projection system 56 is substantially containedwithin a housing 100 which is mounted in the front portion of the upperblade guard 48. The laser barrel 86 (See FIG. 2) is mounted behind alaser assembly cap 102 and is oriented to project downward onto theworkpiece 14. The laser assembly cap 102 has a pair of slotted holes 104through which two screws 106, 108 pass to anchor the cap 102 to thehousing 100. By loosening the screws 106, 108, the laser assembly cap102 can be rotated so that the optical alignment marker 12 may be movedon the workpiece 14 along an axis perpendicular to the blade 36,illustrated by arrows "S".

The pivot pin 88 extends through an opening 110 in the front of thelaser assembly cap 102, which allows the laser barrel 86 to be rotatedwithin the housing 100. Rotation of the laser barrel 86 via the pivotpin 88 allows adjustment of the parallelism of the optical alignmentmarker 12 with respect to the blade 36, illustrated by arrows "R".

The housing 100 has a series of slide grooves 112 which engage with apair of slide rails 114 on a slide plate 116. The slide plate 116 ismounted inside the upper blade guard 48. By pressing the left push knob70 or right push knob 68 (See FIG. 1), the operator can move the lightprojection system 56 laterally in the direction "L". The lateralmovement of the light projection system 56 allows the alignment marker12 to be located on either side of the blade 36. In its preferredoperation, the light projection system 56 is pressed completely to oneside or the other until it engages the end stops 72, 74. However, itwill be appreciated that the lateral adjustment system of the presentalignment invention permits the light projection system 56 to be locatedat any position along the travel of the slide plate 116.

As previously discussed, the preferred light projection system 56generates an optical alignment marker 12 which is 0.030" wide. Since thealignment marker 12 is narrower than the width 37 (See FIG. 4) of theblade 36, it is possible to position the light projection system 56along the edge of the blade 36, so that the blade 36 partially obstructsthe alignment marker 12 and the unobstructed portion of the alignmentmarker 12 accurately indicates where the side of the blade 36 willengage the workpiece 14.

Alternatively, it may be desirable for the alignment marker 12 to bewider than the width 37 of the blade 36. By centering the wide alignmentmarker 12 over the blade 36, the blade 36 will obstruct the centerportion of the alignment marker 12 and the unobstructed portions willaccurately indicate where both sides of the blade 36 will engage theworkpiece 14. It will be understood that a more powerful laser (approx.10-20 milliwatts) may be required to accomplish this alternateembodiment.

The housing 100 is mounted to the slide plate 116 by a pair of housingscrews 118, 120 which pass through a pair of laterally slotted openings122, 124 that allow the housing 100 to be moved in the lateraldirection. Preferably, a pair of biasing springs 126 are interposedbetween the slide plate 116 and the housing 100 to secure the lightprojection system 56 at a particular location. The biasing springs 126preferably generate approximately 8 lbs. of force. It will be understoodby those skilled in the art that a variety of systems could be used toretain the light projection system 56 in a particular position. It alsowill be appreciated that the light projection system 56 of FIG. 3 may beenclosed within an exterior housing (not shown) so that it may beattached to any suitable surface on a miter saw.

FIG. 4 illustrates a top sectional view of preferred miter saw 10. Asdiscussed above, the preferred support spring 32 is located internallyto the support coupling 30. However, it will be understood that avariety of configurations are possible. FIG. 4 also illustrates the slit58 in the lower blade guard 50 through which the optical alignmentmarker 12 preferably passes. A cover plate 128 is included on the upperblade guard 48 for providing access to a blade flange 132 and blade bolt134. The cover plate 128 is held secure to the upper blade guard 48 by apair thumbscrews 134.

The preferred motor 34 contained within a motor housing 136 has anelongated motor shaft 138 supported by a pair of motor shaft bearings140, 142. One end of the shaft preferably has a series of machinedgrooves 144 that operate as a motor pulley 146 for engaging a drive belt148. The outside diameter of the preferred motor pulley 146 is 0.468".

A blade pulley 150 is coupled to the blade 36 by an elongated bladeshaft 152. The outside diameter of the blade pulley is preferably 1.410"and contains a series of grooves which correspond to the motor pulley146. The blade shaft 152 is also supported by a pair of blade shaftbearings 154, 156. The elongated motor and blade shafts 138, 152 providesupport to counteract the torque caused by the drive belt 148. The motorpulley 146 and blade pulley 150 combination preferably provides a 3:1reduction. The motor 34 preferably runs at between 17,000-19,000 rpm'sand the 3:1 reduction of the pulleys 138, 152 causes the blade 36 to runat a no-load speed of approximately 5600 rpm's.

The blade 36 is anchored to the blade shaft 152 by the blade flange 132and blade bolt 134. Underwriters Laboratories specifies that the bladeflange 132 must be at least 1.75" in diameter. In the preferredembodiment of the pulley system invention, the portion of the bladehousing 40 proximate the blade pulley 150 is generally the same diameteras the blade flange 132 so that the blade pulley 150 and belt housing 40do not reduce the cutting radius of the blade 36.

It will be understood by those skilled in the art that the smalldiameter of the motor pulley 146 will create extreme heat on the drivebelt 148. Applicants have found that a drive belt 148 constructed ofKevlar® (low yarn density) provides large force transmission withoutbeing damaged by the corresponding heat. The preferred belt of thepresent invention is available from Circular Technologies of Boulder,Colo.

Turning now to FIG. 5, which is a sectional view of FIG. 4, thepreferred pulley tensioning system 38 comprises a first rigid member 158and a second rigid member 160 with opposing beveled surfaces 162interposed between the blade bearing 154 and the motor bearing 140. Thesecond rigid member 160 is preferably stationary. The first rigid member158 is allowed to move in the direction "X" so that relative movement ofthe beveled surfaces 162 increases or decreases the force in thedirection "F". Rubber plugs 164 are provided to secure the outer surfaceof the bearings 140, 142, 154, 156, to the motor housing 136.

A tension adjustment screw 166 having a head 168, a threaded portion 170and a wear plate 172 may be attached to the first rigid member 158through a slotted opening 174 in the motor housing 136. Rotation of thetension adjustment screw 166 in the clockwise direction moves the firstrigid member 158 toward the head 168 of the tension adjustment screw166, whereby the distance between the blade bearing 154 and the motorbearing 140 is increased. The wear plate 172 allows the tensionadjustment screw 166 to move within the slotted opening 174. Referringagain to FIG. 4, a set screw 176 with a nylon tip is provided to preventthe pulley tensioning system 38 from moving due to vibration.

In the preferred belt tensioning system 38, a total of 0.090" ofadjustment is available. Approximately 0.060" is used for putting on ortaking off the drive belt 148. The remaining 0.030" is available fortensioning the belt 148 as it stretches. It will be understood that theadjustment range of the belt tension system 38 may vary depending on thelength and construction of the belt, the type of pulleys, etc.

Applicants have found that the tensioning system 38 of the presentpulley system invention extends the life of the drive belt 148, sinceadditional tension can be placed on the belt 148 as it wears andstretches over time. Further, belt tensioning system 38 allows the drivebelts 148 to be manufactured to a looser tolerance, thereby decreasingits manufacturing cost.

It will be understood by those skilled in the art that the presentinventions are not limited to the examples discussed above, but may bechanged or modified without departing from the spirit or scope of theinvention. It will be understood by those skilled in the art that a widevariety of miter saw configurations may incorporate the light projectionsystem or adjustable pulley system of the present invention. Further, itwill be recognized that the light projection system of the presentalignment invention may be attached to any suitable surface on the mitersaw.

We claim:
 1. A miter saw with an optical system for projecting anoptical alignment marker onto a workpiece, comprising:a base; aturntable rotatably supported by the base, the turntable having a frontand rear portion; a fence disposed above the base for supporting theorientation of the workpiece located on the base; a support coupled tothe rear portion of the turntable; cutting means including a blade forcutting the workpiece, the cutting means being pivotally coupled to thesupport for positioning the blade from a raised position above theworkpiece to an operational position for engagement with the workpieceto an operational position for engagement with the workpiece, the bladehaving a radius, two sides, and a width and the cutting means having afront and rear portion; and light projecting means attached to thecutting means for projecting a planar beam of light past one side of theblade and onto the workpiece in order to form a linear optical alignmentmarker on the workpiece, the linear optical alignment marker having athickness and two sides, the light projection means further comprisingadjustment means for adjusting the alignment marker so that the side ofthe alignment marker facing the blade is coincident with a plane definedby the one side of the blade, whereby the side of the linear opticalalignment marker that is coincident with the plane defined by the oneside of the blade will designate the location at which the one side ofthe blade will enter the workpiece.
 2. The apparatus of claim 1 whereinthe light projection means comprises laser means for projecting acoherent beam of visible light.
 3. The apparatus of claim 2 wherein thelaser means includes optical means comprising a line generator forconverting the beam into a linear alignment marker having generallylinear configuration substantially parallel to the blade.
 4. Theapparatus of claim 3 wherein the length of the linear alignment markergenerally corresponds to the distance from the front to the rear portionof the turntable when the blade is in the raised position.
 5. Theapparatus of claim 2 wherein the laser means includes sensor means forsensing high temperature and low temperature conditions and forterminating operation of the laser means in response to temperaturesabove the high temperature condition or below the low temperaturecondition.
 6. The apparatus of claim 1 wherein the adjustment meansincludes means for adjusting the special relationship between theoptical alignment marker and the blade.
 7. The apparatus of claim 1wherein the adjustment means includes rotational adjustment means formoving the location of the optical alignment marker on the workpiecealong an axis perpendicular to the blade.
 8. The apparatus of claim 1wherein the adjustment means includes rotational adjustment means forrotating the light projection means in order to adjust the parallelismof the optical alignment marker with respect to a side surface of theblade.
 9. The apparatus of claim 1 wherein the adjustment means includeslateral adjustment means for moving the light projection means along anaxis perpendicular to the blade.
 10. The apparatus of claim 9 whereinthe lateral adjustment means comprises slide means for sliding the lightprojection means laterally.
 11. The apparatus of claim 9 wherein thelateral adjustment means includes biasing means for securing the lightprojection means at a particular location.
 12. The apparatus of claim 9wherein tho lateral adjustment means includes end stops to limit thelateral movement of the light projection means.
 13. The apparatus ofclaim 9 wherein the lateral adjustment means comprises means foradjusting the lateral position of the light projection means to bepositioned generally along one side of the blade so that the width ofthe blade obstructs a portion of the alignment marker and theunobstructed portion of the alignment marker identifies the locationwhere at least one side of the blade will engage the workpiece.
 14. Theapparatus of claim 1 wherein the light projection means is locatedproximate the front portion of the cutting means.
 15. The apparatus ofclaim 1 wherein the cutting means includes an upper guard and the lightprojection means is located within the upper guard.
 16. The apparatus ofclaim 15 wherein the light projection means is located within the upperguard proximate the front portion of the cutting means.
 17. Theapparatus of claim 16 wherein the cutting means includes a lower guardwith a front portion and a rear portion located generally between thecutting means and the turntable, the front portion of the lower guardhaving a slit opening through which the optical alignment marker may beprojected onto the workpiece.
 18. A miter saw with an optical system forprojecting an optical alignment marker onto a workpiece, comprising:abase; a turntable rotatably supported by the base, the turntable havinga front and rear portion; a fence disposed above the base for supportingthe orientation of the workpiece located on the base; a support coupledto the rear portion of the turntable cutting means including a blade forcutting the workpiece, the cutting means being pivotally coupled to thesupport for positioning the blade from a raised position above theworkpiece to an operational position for engagement with the workpiece,the blade having a radius, a first side, a second side, and a width andthe cutting means having a front and rear portion; and light projectionmeans attached to the cutting means for projecting a planarbeam of lightpast either the first or the second side of the blade and onto theworkpiece in order to form a linear alignment marker on the workpiecealong a selected side of the blade, the linear optical alignment markerhaving a thickness and two sides, the light projection means furthercomprising adjustment means for selectably adjusting the alignmentmarker so that the side of the alignment marker facing the selected sideof the blade is coincident with a plane defined by the selected side ofthe blade, whereby the side of the linear optical alignment marker thatis coincident with the plane defined by the selected side of the bladewill designate the location at which the selected side of the blade willenter the workpiece.
 19. A miter saw with an optical system forprojecting an optical alignment marker onto a workpiece, comprising:abase; a turntable rotatably supported by the base, the turntable havinga front and rear portion; a fence disposed above the base for supportingthe orientation of the workpiece located on the base; a support coupledto the rear portion of the turntable; cutting means including a bladefor cutting the workpiece, the cutting means being pivotally coupled tothe support for positioning the blade from a raised position above theworkpiece to an operational position for engagement with the workpiece,the blade having a radius, two sides, and a width and the cutting meanshaving a front and rear portion; and light projection means attached tothe cutting means for projecting a beam of light past at least one sideof the blade and onto the workpiece in order to form an opticalalignment marker on the workpiece, the alignment marker facing the atleast one side of the blade, the light projection means furthercomprising adjustment means for adjusting the beam of light so that aparticular portion of the alignment marker is coincident with a planedefined by one side of the blade, whereby the location of the particularportion of the alignment marker that is coincident with the planedefined by the one side of the blade designates the location at whichthe one side of the blade will enter the workpiece.